Accidental falls are one of the primary causes of disabling injuries to individuals, especially those of advantaged age, and those suffering from physical infirmities. The exposure to falls is particularly acute in the winter season, when snow and ice adds to the problem. The hazard is aggravated, for example, by the presence of ice and snow on such surfaces as walkways, ramps, entranceways, helicopter pads and similar places, and while attempts are normally made to keep these locations clear of accumulations, it is not always possible or convenient to do so.
Furthermore, "passive" measures to prevent snow and ice accumulations such as, for example, the distribution of salt, sand and similar materials on the surfaces to be protected are not always effective, due to temperatures below that at which salt is effective because of additional accumulations of snow and ice, or for other reasons.
In the past, it has been proposed to employ certain "active" methods for eliminating snow and ice on such surfaces.
U.S. Pat. No. 2,912,555, for instance, shows a heating assembly comprising an insulating board laced with electrical heating wire.
U.S. Pat. No. 2,997,568 describes a heating element intended for embedding in concrete consisting of wire mesh to which electrical heating wire is attached.
U.S. Pat. No. 3,047,701 teaches a layered heating assembly, also designed for embedding in concrete.
U.S. Pat. No. 3,193,664 illustrates another electrical heating element intended for embedding in concrete slabs.
U.S. Pat. No. 3,209,128 details a still further heating mat intended for embedding in concrete.
U.S. Pat. No. 3,244,858 reveals a rigid panel having electrical wires embedded therein, used for a variety of heating requirements.
U.S. Pat. No. 3,812,320 is directed to a mat heated with electrical wires, which is provided with heat distributing interior chambers.
U.S. Pat. No. 3,967,855 involves formation of a thermoplastic sheet provided with multiple grooves into which electrical resistance elements are forced.
While some of the preceding devices address problems similar to those which the invention herein disclosed seeks to eliminate, many of the devices described are not portable; others comprise permanent installations which are difficult to maintain and repair, while still others are impractical insofar as the removal of ice and snow from large areas is concern.